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QTOF Analysis Has Wide Scope

Photonics.comSep 2007
ZURICH, Switzerland, Sept. 10, 2007 -- A method involving a quadrupole time-of-flight (QTOF) mass spectrometer enables large numbers of samples to be analyzed quickly and economically, according to a group led by Renato Zenobi, professor of analytical chemistry at the Organic Chemistry Laboratory of the Swiss Federal Institute of Technology, or ETH Zurich (Eidgenössische Technische Hochschule Zürich).

The method will make comprehensive monitoring of food quality, among other applications, possible in settings such as warehouses. The procedure may have prevented situations such as when German police discovered about 50 tons of spole meat on the premises of a wholesaler in Bavaria last August, they said.

The group's research, published in a recent issued of the scientific journal Angewandte Chemie, is a further development of another method recently published by the group that detected various substances in the breath. Using the new enhanced method, they said, they can now also very precisely track down substances on surfaces of any kind. ,br>Both methods are based on a QTOF mass spectrometer, which are commonly used in detection applications today. Nortmally, samples for QTOF mass spectrometry are normally presented in solution. The solution is electrosprayed, with the additional aid of a desolvation gas. The tiny droplets give rise to ions that are characteristic of the substance to be analyzed and which the QTOF instrument measures.

The researchers said they have turned the principle nearly on its head: Instead of studying the substances in the solution, they now examine the substances present in the desolvation gas assisting the spray. With the newmethod, nitrogen is blown from a small nozzle onto a sample surface. As the gas strikes the surface it desorbs semi-volatile substances. The “enriched” gas stream is then fed into the mass spectrometer where the absorbed substances can be precisely analyzed.

Zenobi said there is "nothing special" about the new method from a technical standpoint. "Huanwen Chen, who developed the method during his postdoctoral studies in Zenobi’s group, impressively demonstrated this when, together with his supervisor, he presented the new method to a company. Within one hour, Chen had modified their mass spectrometer so it could be used to analyze the surface of any kind of object."

The remarkable aspect of the new method is the wide variety of possibilities it opens up, Zenobi said. "One particular strength of our approach is that even the surfaces of living organisms can be examined. It only takes a few seconds to measure a single sample; so large numbers of random samples can be routinely analyzed."

Zenobi said the sample material -- for example, meat samples -- doesn't even need to be thawed.

The studies carried out by the researchers on the skin of various test subjects lead in quite a different direction, he said. Traces of nicotine, coffee and explosives could all be detected on the skin. According to Zenobi , "The method’s strength is that it is fast and noninvasive, and needs no special sample preparation." He said many potential applications exist in food technology, safety and medicine.

A device used to measure the masses and relative concentrations of atoms and molecules. It utilizes the Lorentz force generated by external magnetic field on a moving charged particle, in which the particles are deflected by the magnetic field according to their masses. Once deflected, the particles are detected and recorded electrically to provide a mass spectrum of the input beam of ions.

The technology of generating and harnessing light and other forms of radiant energy whose quantum unit is the photon. The science includes light emission, transmission, deflection, amplification and detection by optical components and instruments, lasers and other light sources, fiber optics, electro-optical instrumentation, related hardware and electronics, and sophisticated systems. The range of applications of photonics extends from energy generation to detection to communications and...